The embodiments herein relate generally to hydraulic fracturing operations and, more particularly, relate to crosslinker-coated particulates capable of suspending in treatment fluids comprising gelling agents.
Subterranean wells (e.g., hydrocarbon producing wells, water producing wells, and the like) are often stimulated by hydraulic fracturing treatments. In hydraulic fracturing treatments, a gelled treatment fluid is pumped into a portion of a subterranean formation at a rate and pressure such that the subterranean formation breaks down and one or more fractures are formed therein. Particulate solids, such as graded sand, are typically suspended in at least a portion of the treatment fluid and deposited into the fractures in the subterranean formation. These particulate solids, or “proppants particulates” (also referred to simply as “proppants”) serve to prop the fracture open (e.g., keep the fracture from fully closing) after the hydraulic pressure is removed. By keeping the fracture from fully closing, the particulates aid in forming conductive paths through which produced fluids, such as hydrocarbons, may flow.
Hydraulic fracturing treatments may also be combined with sand control treatments, such as a gravel packing treatment. Such treatments may be referred to as “frac-packing” treatments. In a typical frac-packing treatment, a gelled treatment fluid comprising a plurality of particulates (e.g. is pumped through the annulus between a wellbore tubular mounted with a screen and a wellbore in a subterranean formation. The fluid is pumped into perforations through a casing, or directly into the wellbore in the case of open hole completions at a rate and pressure sufficient to create or enhance at least one fracture, and the particulates are deposited in the fracture and in the annulus between the screen and the wellbore. The particulates aid in propping open the fracture, as well as controlling the migration of formation fines or other loose particles in the formation from being produced with produced fluids.
The degree of success of a fracturing operation (both a traditional hydraulic fracturing operation and a frac-packing operation) depends, at least in part, upon fracture porosity and conductivity once the fracturing operation is complete and production is begun. Fracturing operations may place a volume of particulates into a fracture to form a “proppant pack” or “gravel pack” (referred to herein as “proppant pack”) in order to ensure that the fracture does not close completely upon removing the hydraulic pressure. The ability of the particulates to maintain a fracture open depends upon the ability of the particulates to withstand fracture closure pressures. The porosity of a proppant pack within a fracture is related to the interconnected interstitial spaces between abutting particulates. Thus, the fracture productivity is closely related to the strength of the placed particulates and the interstitial spaces between the particulates in the proppant pack.
In some fracturing operations, a large volume of particulates may be placed within the fracture to form a tight proppant pack. In other fracturing operations, a much reduced volume of particulates may be placed in the fracture to create larger interstitial spaces between the individual particulates. However, both fracturing approaches may result in at least some settling of the particulates within a treatment fluid as the treatment fluid is introduced downhole or after placement in a fracture opening. Particulate settling may lead to a fracture or a top portion of a fracture closing, which may lower the conductivity of the proppant fracture and result in proppant masses having little or no interstitial spaces at the bottom portion of a fracture, thereby further decreasing the conductivity of the fracture. Proppant settling may be particularly problematic in cases where proppant aggregates are used in place of traditional proppant particulates because the proppant aggregates tend to be larger and may be heavier and, thus, more difficult to hold in suspension. While settling may be counteracted by using a high pump rate or by increasing the viscosity of the fluid carrying the proppant particulates or proppant aggregates, such methods often lose effectiveness once the fluid comprising the proppant or aggregates is placed into a fracture and before the hydraulic pressure is released.